The asymmetric unit of the title compound, [Ni2(C16H14N2O2)2], contains an NiII cation which is coordinated by two imine N atoms and by two phenolate O atoms of the salen ligand {salen = N,N′-bis(salicylidene)ethane-1,2-diamine or 2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenol}, leading to a distorted square-planar conformation. When a secondary Ni—O interaction > 2.41 Å to the neighbouring phenolate O atom is considered, two molecules are linked into a centrosymmetric dimer with an overall square-pyramidal coordination for the NiII cation. Weak π–π interactions with a shortest interplanar distance of 3.704 Å help to stabilize the crystal structure.